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Odor - An Emerging Concern for Producers

By G. Tom Tabler, Center of Excellence for Poultry Science at the University of Arkansas's Avian Advice - Agricultural odors are an unavoidable part of livestock production and are emitted from every poultry operation. These odors along with the growth of the poultry industry have sparked debate, concern and action in many U.S. communities.
calendar icon 3 July 2006
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Odor - An Emerging Concern for Producers - By G. Tom Tabler, Center of Excellence for Poultry Science at the University of Arkansas's Avian Advice - Agricultural odors are an unavoidable part of livestock production and are emitted from every poultry operation. These odors along with the growth of the poultry industry have sparked debate, concern and action in many U.S. communities.


Air and water quality have become major issues, along with social and economic concerns. These concerns stem from the fact that the difference between “the city” and “the country” is becoming increasingly difficult to distinguish.

Today, a rural family is not necessarily an agricultural family. The gap is wide between an agricultural family that understands that odors are a part of production agriculture and a rural family that recently moved from the city with little or no tolerance for agricultural odors. Therefore, it is important that poultry producers have a basic knowledge of odor control strategies and do their best to accommodate non-farming neighbors.

Odor Causes

Some odors are generated by the poultry or livestock themselves, and some by the feed, but the most objectionable odors arise from manure and manure decomposition. More than 200 odor-generating compounds have been identified from microbial decomposition of manure (Pfost et al., 1999). This means that the intensity of the odor depends upon microbial growth and that growth rate will vary with moisture content, pH, temperature, oxygen concentration, and other environmental factors. This is illustrated by the fact that, as temperatures decrease with onset of cooler, autumn conditions, microbial activity slows, which is why odors are generally less noticeable in the cooler months. Yet odors vary greatly, and the offensiveness of each odor is dependent upon the person(s) smelling the odor.

Poultry and livestock odors originate from three primary sites or activities: 1) livestock facilities and the housed livestock within, 2) manure storage facilities, and 3) land application of manure. While land applying (spreading) poultry litter is a common practice in many areas, be aware that most odor complaints are associated with land application of manure, not storage facilities or housing. As rural areas continue to fill with an increasing exodus from the cities, litter application will become an even greater concern. Expect additional legal involvement and plan ahead for increased regulation of land application of poultry litter generated by your operation.

A serious detrimental component of odor is dust, which can be carried long distances on air currents. Dust particles act as a transport mechanism for odor. Land applying poultry litter often creates significant quantities of dust, which may travel as far as several miles or as little as several feet. Wind direction and speed are constantly changing, which can greatly affect dust and odor patterns making it difficult to predict the impact odors and dust will have on residents in areas surrounding a livestock enterprise.

Understanding Odor

Several different criteria may be used to evaluate odors. Familiarity with these parameters will help producers better understand odor source and interpret odor data. Odors are most commonly evaluated in terms of concentration (threshold), intensity, persistence (Table 1). These three variables are often used to provide regulatory and scientific personnel with some measurement of odor potency and how long the odor is likely to remain. Hedonic tone and character are more subjective measurements that are not typically used for regulatory purposes (Sheffield and Bottcher, 2000).

The amount of odor emitted from a particular farming operation is a function of animal species, housing types, manure storage and handling methods, size of the odor sources, and the implementation of odor control strategies (Nicolai and Pohl, 2005). A variety of strategies and innovative technologies are available for odor control. Some work better for liquid-type wastes (lagoons) while others are equally effective for both liquid and dry manure situations. Technologies that capture and treat odors include manure storage covers, organic mats, and biofilters. Technologies capable of dispersing or masking odors include vegetative windbreaks, windbreak walls, proper site selection, adequate setback distances and deodorant and masking agents. However, before adopting any method, producers should consider applicability, effectiveness, costs, and labor or management requirements of all available technologies.

Be Proactive

Most people today are generations removed from the farm and have little or no association to agriculture. Therefore, to most of the general public, this lack of association means that in their thinking agriculture continues to decline in importance. Their only relationship to the poultry industry may be to complain about dust, odors, noise, or someone spreading litter, which leaves a negative impression of poultry farming. Producers should be aware of that perception is reality for many people, particularly folks with no understanding of modern agriculture.

In addition, producers should understand that those people’s perception has a large influence on their opinions and actions. This is especially true with regard to the appearance of poultry production facilities. Visual perception has a huge influence on how much or how little people will accept before a complaint occurs. Well-maintained production units usually are not perceived to smell as bad as units that look uncared-for and run-down. Production sites that appear to be overgrown with weeds and that has junk scattered everywhere are more likely to generate a complaint than sites that are nicely landscaped with regularly mown lawns and an attractive appearance.

Livestock farmers in the U.S. are under increasing pressure to reduce odor emissions from their property and must become more proactive in addressing the issue. However, the current financial environment dictates that farmers identify control strategies that can be implemented with minimal cost. For example, the planting of trees around farmland or buildings has been identified as a potentially effective, low-cost measure to enhance ammonia recapture at the farm level and reduce long-range atmospheric transport (Theobald et al., 2001).

Properly planted and well-maintained windbreaks can serve a number of functions. Windbreaks that shield poultry houses from the view of passers-by may decrease the chance of odor complaints since people who cannot see the source of an odor, they are less likely to: 1) notice the odor in the first place and 2) complain about it. Windbreaks cause the air to be lifted up and over the windbreak, which causes mixing of fresh air with odorous air, thus diluting the odor effect. Well laid-out and landscaped windbreaks also increase property values. In addition, planting trees and shrubs is perceived in a positive manner and demonstrates a producer’s commitment to protecting our environment.

Many nuisance complaints occur shortly after litter has been land applied. Producers should carefully select the time when litter will be spread. Let neighbors know when you plan to spread litter. Keep an open line of communication with anyone who may be affected by the spreading of litter from your operation. Avoid weekends and holidays, pay attention to wind direction, and once started, finish as soon as possible so that you limit the generation of dust and odor.

Spread litter during the morning as much as possible because as air warms it will rise, which lifts odors upward for mixing and dilution with fresh air as well as drying litter. While your cooperative public attitude will have little effect on the actual odor, it may be very important in avoiding complaints against your farming operation. Neighbors are less likely to complain if they know you are aware and attempting to address their concerns. Always be courteous when dealing with neighbors, even if you may be unable to comply with all their wishes. In short, be a good neighbor.


Given the continuing urbanization of rural areas and the level of livestock intensification in the U.S., it appears likely that complaints associated with agricultural odors will increase. Increased regulations have drastically changed livestock production practices in many parts of Europe and could do so in this country as well. Poultry producers need to understand the causes of odors and apply basic odor control principles in their daily management routines. Odor control need not be difficult or expensive and, in fact, can start with something as simple as running an attractive operation, keeping the grass and weeds cut, projecting a positive image, and being a good neighbor.

Address the potential concerns of your neighbors before they escalate into complaints, or restrictive regulations that may determine whether or not you are allowed to remain in business. The continued viability of poultry production in some areas is increasingly dependent upon a community’s willingness to accept the industry as a responsible corporate citizen.


Nicolai, R., and S. Pohl. 2005. Understanding livestock odors. Cooperative Extension Service Fact Sheet FS 925-A. South Dakota State University, Brookings, SD.
Pfost, D. L., C. D. Fulhage, and J. A. Hoehne. 1999. Odors from livestock operations: Causes and possible cures. Outreach and Extension Pub. # G 1884. University of Missouri-Columbia.
Sheffield, R., and R. Bottcher. 2000. Understanding livestock odors. Cooperative Extension Service Pub. # AG-589. North Carolina State University.
Theobald, M. R., C. Milford, K. J. Hargreaves, L. J. Sheppard, E. Nemitz, Y. S. Tang, V. R. Phillips, R. Sneath, L. McCartney, F. J. Harvey, I. D. Leith, J. N. Cape, D. Fowler, and M. A. Sutton. 2001. Potential for ammonia recapture by farm woodlands: design and application of a new experimental facility. In: Optimizing Nitrogen Management in Food and Energy Production and Environmental Protection: Proceedings of the 2nd International Nitrogen Conference on Science and Policy. The Scientific World 1(S2):791-801.

Source: Avian Advice - Summer 2006 - Volume 8, Number 1